Electrolytic production of dichloroformoxime



Dec. 22, 1959 MADAUS ET AL 2,918,418

ELECTROLYTIC PRODUCTION OF DICHLOROFORMOXIME Filed Oct. 9, 1956 PUMP N John H. Modous Herman B.Urlb0C INVENTORS MAKE UP ELECTROLYTE ATTORNEYS United States Patent ELECTROLYTIC PRODUCTION OF DICHLORO- FORMOXIME John H. Madaus and Herman B. Urbach, Niagara Falls,

N.Y., assignors to Olin Mathieson Chemical Corporation, a corporation of Virginia Application October 9, 1956, Serial No. 614,972

2 Claims. (Cl. 204-74) This invention relates to a method for the production of dichloroformoxime and, in particular, to the production of dichloroformoxime by the electrolytic reduction of chloropicrin in an alcohol-sulfuric acid electrolyte followed by the recovery of the dichloroformoxime from the complex electrolyte by a procedure involving extraction with chloropicrin.

Methods previously advanced (reference: Der Verlauf der kathodischen Reduktion von Trichloronitrometban, Zeitschrift fiir Elektrocbemie, 53, No. 3, pp. 109-113, May 1949) for the electrolytic reduction of chloropicrin to dichloroformoxime in a methanol-sulfuric acid electrolyte have suffered from the disadvantage that the yield of dichloroformoxime falls oil after 75 per cent of the theoretically required amount of electricity necessary for complete conversion has been passed. The further reduction of the dichloroformoxime to undesirable products is responsible for the decrease in yield with the passage of more current. This invention permits the continuous removal of the dichloroformoxime produced in such a system thereby preventing further reduction to unwanted products.

By the process of this invention, an electrolyte consisting essentially of a solution of an alcohol, namely, methanol or ethanol or a mixture thereof, and sulfuric acid saturated with chloropicrin is continuously electrolytically reduced in a suitable cell. The electrolyte is passed into the cell in the space between the cathode and the diaphragm separating the catholyte compartment from the anolyte. Alcohol-sulfuric acid-chloropicrin-dichloroformoxime solution is withdrawn from the catholyte compartment of the cell and is extracted in a first extraction step with chloropicrin which is saturated with sulfuric acid and methanol or ethanol or a mixture of methanol and ethanol. in this extraction step, the dichloroformoxime distributes itself between the two immiscible phases, the first phase being an electrolyte phase reduced in dichloroformoxime content and saturated with chloropicrin and the second phase being chlolopicrin containing dichloroformoxime. By the use of this first extraction step, the concentration of the dichloroformoxime in the electrolyte can be maintained at an optimum value by circulating the electrolyte containing the dichloroformoxime to the extraction step and then returning the electrolyte reduced in dichloroformoxime content and saturated with chloropicrin to the cell.

The chloropicrin phase produced in the first extraction step, enriched in dichloroformoxime, is then passed to a second extraction step wherein the chloropicrin phase is extracted with water. When this is done, the chloropicrin phase becomes reduced in dichloroformoxime content and is returned to the first extraction step. Because of the heat sensitivity of the dichloroformoxime-water solution, it is not possible to distill the dichloroformoxime from the water-dichloroformoxime solution. Therefore, a third extraction step is carried out in which the waterdichloroformoxime solution is countercurrently extracted with a lower dialkylether containing from 2 to 4 carbon ample can be carried out.

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atoms in each alkyl radical, for example, diethyl-ether or diisopropylether. This third extraction step results in the production of a water phase which is decreased in dichloroformoxime content, and this phase can be returned to the second extraction step in whole or in part or discarded in whole or in part. The third extraction step also results in the production of an ether phase of increased dichloroformoxime content, and dichloroformoxime product can be recovered from this phase by distilling the ether overhead and recovering pure dichloroformoxime as bottoms. If desired, ether distilled in this step can be recovered and again be employed in the third extraction step.

The composition of the electrolyte fed to the electrolytic reduction cell can be widely varied, the composition of the electrolyte generally comprising from 10 to 60 weight percent of chloropicrin, from 5 to 35 weight percent of sulfuric acid and from 25 to 65 Weight percent of methanol, ethanol or mixture thereof. The voltage of the cell can also be varied widely, depending upon the composition of the electrolyte. In general, the voltage across the cell will be from 10 to 30 volts, the current density will be of the order of milliamperes per square centimeter, and the cell will be operated at a temperature within the range from about 5 C. to about +25 C. The electrodes used in the cell can be any of a wide variety of metals, such as platinum, brass, tin, copper, tin backed with copper, tin backed with brass, and the like. Countercurrent extraction columns are preferably employed in each of the extraction steps, such as columns being divided with various packings in order to give turbulent flow, and each of the extraction steps will generally be conducted at a temperature Within the range from about 20 to about 50 C.

Dichloroformoxime when dissolved in Water and refiuxed at 54-53 C. (28 millimeters: of mercury pressure) for from 2 to 3 hours will provide an aqueous solution of pure hydroxyl amine hydrochloride which can be evaporated at reduced pressure to give a good yield of especially pure hydroxyl amine hydrochloride. Hydroxyl amine hydrochloride is a useful photographic developer and can also be utilized in a wide variety of organic synthesis. Dichloroformoxime, also known as phosgene oxime, can also be used as a military poison gas and in various organic synthesis.

Example This example is to be considered in conjunction with the accompanying drawing, which illustrates diagrammatically, an arrangement of apparatus in which the ex- In general, the method employed for the manufacture of dichloroformoxime by electrolytic reduction is that suggested by Brintzinger, Ziegler and Schneider (reference: Der Verlauf der kathodischen Reduktion von Trichlornitromethan, Zeitschrift fiir Elektrochemie, 53, No. 3, pp. 109-113, May 1949).

Referring now to the drawing the numeral 1 represents a diaphragm cell provided with diaphragm 2 which is a cation exchange membrane made from an ion exchange membrane which is a strongly acidic sulfonated cross-linked polymer of styrene and divinylbenzene and a binder which is polystyrene. The cell is thereby divided into an anode or anolyte compartment 3 and a cathode or catholyte compartment 4. Platinum electrodes 5 and 6 are provided in the anode and cathode compartments, respectively. These electrodes each have an area of 300 square centimeters, are spaced 27 miilllimeters apart and are of a size such that when a voltage of approximately lO-l5 volts im impressed across the cell a current density of approximately 100 milliamperes per square inch is maintained. Anode compartment 3 contains approxi- Patented Dec. 22, a

mately 1000 cc. of electrolyte and cathode compartment 4 contains approximately 1000 cc. of electrolyte.

To the cell 1 there is continuously passed by means of line 7 at the rate of 300 grams per hour an electrolyte'which is saturated with chloropicrin and which is composed of approximately 17.0 weight percent sulfuric acid, 30.0 weight percent methanol and 53.0 weight percent chloropicrin. From the cell, there is continuously withdrawn through line 8, 300 grams per hour of electrolyte containing 1.53 weight percent dichloroformoxime. The major portion of the electrolyte withdrawn (200 grams per hour) is returned to the cell by means of line 9 after having been passed through heat exchanger 10 which is maintained at -78 C. by means of methanol. This is accomplished in part by means of pump 11 and line 12. The portion (100 grams per hour) of the electrolyte which is removed from cell 1 by means of line 8 but which is not returned to the cell by means of lines 9 and 7 passes by means of line 13 into the first extraction step 14, which is a countercurrent extraction column having the equivalent of approximately 12 theoretical plates. This first extraction Zone is operated at'a temperature of approximately 20 C. Into the top of first extraction step 14 by means of line 15 there is introduced 2001.48 grams per hour of a mixture of chloro picrin which is saturated with methanol and sulfuric acid at C. and which contains 0.07 gram per hour of dichloroformoxime. Depleted electrolyte (98.52 grams per hour containing 0.05 gram per hour of dichloroformoxime) is returned to the cell by means of line 16. Make-up electrolyte, composed of 17.0 weight percent of sulfuric acid, 30.0 weight percent methanol and 53.0 weight percent chloropicrin, is introduced into the system by means of line 17 in order to maintain constant cell level.

The chloropicrin phase leaving first extraction zone 14 by means of line 18 flows at the rate of 2001.48 grams per hour and contains 1.48 grams per hour of dichloroformoxime. This phase passes into the top of second extraction step 20, which is a countercurrent extraction column having an equivalent of approximately 6 theoretical plates. Also into second extraction step 20 there is introduced by means of line 21, 2000 grams per hour of water. The operating conditions in second extraction step 20 are such that the temperature is maintained at approximately 20 C. From the bottom of the second extraction step 20 through line 15, there is withdrawn 2000.07 grams per hour of chloropicrin phase containing 0.07 gram per hour of dichloroformoxime, and this stream is introduced into the first extraction step 14.

Water-dichloroformoxime phase (2001.41 grams per hour containing 1.41 grams per hour of dichloroformoxime) is removed from the top of the second extraction step 20 by means of line 22 and is passed into the top of third extraction step 23, which is a countercurrent extraction column containing the equivalent of approximately 6 theoretical plates. Into the bottom of the third extraction step 23 there is introduced by means of line 24, 340 grams per hour of diethylether, the conditions in the third extraction step being such that the temperature is maintained at approximately 20 C. From the bottom of third extraction step 23 through line 25 there is removed 2000 grams per hour of water and 140 grams per hour of diethylether, the diethylether being dissolved in the water. This mixture passes into still 26, from the top of which overhead a vapor mixture composed of 139.5 grams per hour of diethylether and 0.5 gram per hour of water is introduced into third reaction step 23 by means of lines 27 and 24 and from the bottom of which through line 21 there is withdrawn 2000 grams per hour of water. From the top of the third extraction zone 23 by means of line 28 there is removed a mixture consisting essentially of 200 grams per hour of diethylether and 1.34 grams per hour of dichloroformoxime, for a total of 201.34 grams per hour. This mixture enters drying tower 29 wherein it is dried by contact with sodium sulfate. The dried mixture then passes by means of line 30 into ether still 31 which is operated at a pressure of approximately mm. of mercury. Overhead from still 31 there is removed by means of line'32, 200 grams per hour of diethylether and approximately 0.01 gram per hour of dichloroformoxime. Also. from still 31 there is removed by means of line 33, 1.33 grams per hour of dichloroformoxime product in the form of bottoms. In order to provide makeup diethylether, 0.5 gram of that material is introduced into the system by means ofline 34 from storage vessel 35.

It is claimed:

1. In a process wherein chloropicrin dissolved in an alcohol-sulfuric acid electrolyte is electrolytically reduced in a diaphragm cell to form dichloroformoxime, the steps of withdrawing electrolyte from the catholyte compartment of the cell, in a first extraction step extracting the Withdrawn electrolyte with chloropicrin saturated with alcohol and sulfuric acid whereby an electrolyte phase reduced in dichloroformoxime content and saturated with chloropicrin and a chloropicrin phase containing dichloroformoxime are formed, returning the electrolyte phase to the catholyte compartment of the cell, in a second extraction step extracting the chloropicrin phase containing dichloroformoxime with water whereby a chloropicrin phase of decreased dichloroformoxime content and a water phase of increased dichloroformoxime content are formed, returning the chloropicrin phase of decreased dichloroformoxime content to the first extraction step, in a third extraction step extracting the water phase with at least one dialkyl ether containing from two to four carbon atoms in each alkyl radical to form a water phase of decreased dichloroformoxime and an ether phase of decreased dichloroformoxime content, and vaporizing the ether from the ether phase to leave a dichloroformoxime residue, said alcohol being selected from the group consisting of methanol and ethanol.

2. The process of claim 1 wherein said alcohol is methanol, wherein said ether is diethyl ether and wherein the water phase formed in the third extraction step is introduced into the second extraction step.

References Cited in the file of this patent Brintzinger et al.: Z. Elektrochemie, 53, 109-13 (19 49).

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,918,418 December 22, 1959 John H. Madaus et a1.

Column 2,

line 70, for "im" read is 50, for "decrea column 4, line sed" read increased Signed and sealed this 19th day of July 1960.

(SEAL) Attes t:

Commissioner of Patents 

1. IN A PROCESS WHEREIN CHLOROPICRIN DISSOLVED IN AN ALCOHOL-SULFURIC ACID ELECTROLYTE IS ELCETROLYTICALLY REDUCED IN A DIAPHRAGM CELL TO FORM DICHLOROFORMOXIME, THE STEPS OF WITHDRAWING ELECTROLYTE FROM THE CATHOLYTE COMPARTMENT OF THE CELL, IN A FIRST EXTRACTION STEP EXTRACTING THE WITHDRAWN ELECTROLYTE WITH CHLOROPICRIN SATURATED WITH ALCOHOL AND SULFURIC AICD WHEREBY AN ELECTROLYTE PHASE REDUCED IN DICHLOROFORMOXIME CONTENT AND SATURATED WITH CHLOROPICRIN AND A CHLOROPICRIN PHASE CONTAINING DICHLOROFORMOXIME ARE FORMED, RETURNING THE ELECTROLYTE PHASE TO THE CATHOLYTE COMPARTMENT OF THE CELL, IN A SECOND EXTRACTION STEP EXTRACTING THE CHLOROPICRIN PHASE CONTAINING DICHLOROFORMOXIME WITH WATER WHEREBY A CHLOROPICRIN PHASE OF DECREASED DICHLOROFORMOXIME CONTENT AND WATER PHASE OF INCREASED DICHLOROFORMOXIME CONTENT ARE FORMED, RETURNING THE CHLOROPICRIN PHASE OF DECREASED DICHLOROFORMOXIME CONTENT TO THE FIRST EXTRACTION STEP, IN A THIRD EXTRACTION STEP EXTRACTING THE WATER PHASE WITH AT LEAST ONE DIALKYL ETHER CONTAINING FROM TWO TO FOUR CARBON ATOMS IN EACH ALKYL RADICAL TO FORM A WATER PHASE OF DECREASED DICHLOROFORMOXIME AND AN ETHER PHASE OF DECREASED DICHLOROFORMOXIME CONTENT, AND VAPORIZING THE EHER FROM THE ETHER PHASE TO LEAVE A DICHLOROFORMOXIME RESIDUE, SAID ALCOHOL BEING SELECTED FROM THE GROUP CONSISTING OF METHANOLA ND ETHANOL. 